If a ligament is torn in the foot, hand, or joint, the surgical procedure used to prevent permanent impairment consists of either restoring the damaged tendon with surgical elements, as described, for example, in Publication Nos. WO-A-96 03084 and EP-A-O 145 492, or replacing the torn ligament with either a substitute biological tendon as described in Publication No. EP-A-O 642 773, or with an auxiliary tendon of less functional importance which can be removed without harming the patient. To do this, the tendon is guided through passageways in the bone which are generally formed as close as possible to the original location of the torn ligament. The tendon then forms either a single loop, a double loop, a figure eight, or some other shape, and replaces the torn ligament. Moreover, in the majority of musculo-tendon transplants performed for various hand and foot pathologies, the transplanted tendon or tendons are removed from a distal insertion point and reinserted at a new location through a passage in the bone. The tendon is inserted through the tunnel, then usually formed into a knot, and sutured either onto itself or directly onto the periosteum.
The major difficulty in these interventions often consists of inserting the tendon through bone passageways that are hardly much larger than the diameter of the tendon, since there may be only small amount of bone in the area, making it impossible to form a larger tunnel. In addition, in order for the tendon to become quickly and solidly integrated within the bone, it is preferable to establish contact as intimately as possible between the bone and the tendon.
The method known in the art, used conventionally, consists of first using a needle to anchor a thread or wire to the end of the tendon. To ensure a tight attachment, the thread is passed through the tendon several times. Next, the thread and the needle attached to it are passed through the bone passageway and finally, the thread is pulled so the tendon will pass through the bone opening.
This method has numerous disadvantages. First, since the thread must pass through the tendon several times, the tendon can be damaged and weakened. This causes more problems, since the tendon is short and its maximum length should be used. Moreover, the structure of a tendon approximately resembles that of a string composed of several threads, all nearly identical in diameter. Because of this structure, the thread is never very solidly anchored, and it often weakens when pulled hard enough to move the tendon through the bone passageway. If the attachment breaks, tendon damage is worsened, and reattachment is very difficult.
In addition, the tunnel formed in the bone is usually fairly approximate, having been made with a simple boring instrument. Often two V shaped holes are made to form the passageways, resulting in highly variable configurations.
On the other hand, needles have a definite configuration which can be modified only slightly by bending them. If the configuration of the bone passageway and the needle do not conform to each other, as is often the case, the needle will not pass through the opening freely. Threading the needle through the passageway becomes even more difficult because its point tends to hook onto the spongy bone forming the walls of the passageway.
At this stage, the surgeon either tries to reshape the needle so it is identical to the passageway, until the needle finally breaks, or tries to shape the bone canal tunnel so it is identical to the needle, which often causes a fracture that makes the bone passageway useless.
Next, once the needle and thread have passed through the opening, the tendon must be led through it in turn. This step often poses the major problem in the intervention. In practice, the end of the tendon which reaches the tunnel entry often does not completely penetrate the tunnel. Pulling the thread may cause the tendon to "explode," enlarging its diameter. Therefore, it is sometimes definitively impossible to complete passage. Pulling harder ultimately breaks the attachment. In all these situations, the tendon becomes damaged and the only way to reattach the tendon is to remove the damaged portion.
At this stage the surgeon often uses various pointed instruments to attempt to force the tendon extremity into the tunnel opening, while pulling harder and harder. It is often at this point, however, that the attachment fails. Sometimes an attempt is made to enlarge the hole, at the risk of provoking a fracture and rendering the passageway useless, or to reduce the tendon diameter, which weakens its resistance.
This method transforms an initially simple intervention into a long procedure, complicated by the use of ill-suited tools.
An attempt has been made to resolve these problems by using a surgical device consisting of a small cone-shaped sheath made of flexible plastic. The tendon is slid inside and then anchored by filaments encasing it from end to end. Thus, theoretically this device facilitates threading the tendon through the bone tunnel.
However, this technique has several disadvantages. More specifically, since the tendon itself requires considerable space, the increased diameter of the sheath-tendon unit can make passage through the bone impossible. Also, once the sheath has been removed, the resulting contact between the bone and the tendon is not ideal.
Moreover, the tendon must be anchored to the sheath with thread. This damages the tendon and takes time to accomplish. Furthermore, when the tendon is removed, the attachment must be severed, whereas if the tendon is attached directly, the extra step is eliminated.
Finally, this technique requires that different types of sheaths be used to accommodate various tendon sizes. In addition, the sheaths are relatively expensive. They are stitched and sterilized several times, they wear out, and they need to be replaced regularly. This technique is therefore quite costly.